Run asynchronous function in R

Question

I have the following code:

myfun <- function() {
  fun2()

  return(1+1)
}

I want fun2() is invoked and then moved to the next lines without waiting for the result. Function fun2 does not return anything and I don't care when it finishes, I just need to launch it. What is the best way to achieve it? Parallel process, multithreading, async call? Any code samples are appreciated.

Answer 1

The future package (I'm the author) provides this:

library("future")
plan(multiprocess)

myfun <- function() {
  future(fun2())

  return(1+1)
}

Unless fun2() is function used purely for its side effects, you typically want to retrieve the value of that future expression, which you do as:

f <- future(fun2())
y <- fun3()
v <- value(f)
z <- v + y

An alternative is to use the %<-% operator as in:

v %<-% fun2()
y <- fun3()
z <- v + y

FYI, if you use

plan(cluster, workers = c("n1", "n3", "remote.server.org"))

then the future expression is resolved on one of those machines. Using

plan(future.BatchJobs::batchjobs_slurm)

will cause it to be resolved via a Slurm job scheduler queue.

Answer 2

Eventually I stopped on the following solution:

Rpath <- Find(file.exists, c(commandArgs()[[1]], file.path(R.home("bin"), commandArgs()[[1]]),
                             file.path(R.home("bin"), "R"), file.path(R.home("bin"), "Rscript.exe")))
out <- system('%s --no-save --slave -e \"Your R code here\" ', wait=FALSE)

The first line searches for the path of R executable, and the second executes R code from the command-line environment not waiting for result.